Spoke-Type IPM Rotor Structure With Hollow Cooling Cavity

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Solution Overview

Problem

Existing rotors for spoke-type internal permanent magnet (IPM) motors incorporate non-magnetic cores that increase production effort, weight, and component count, necessitating a more efficient and lightweight design.

Innovation Solution

The rotor design features a shaft with a coaxially arranged annular rotor body, comprising alternating rotor stack segments and magnets, with a cavity between the shaft and rotor body for air cooling and reduced weight, utilizing separate elements and support rings for stabilization and torque transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a non-magnetic core is used in the rotor, then the structural stability is improved, but the weight increases and production effort increases

Engineering Contradiction:
Improvestructural stabilityVSAvoidrotor weight
Core Design Contradiction:
Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The invention extracts and removes the non-magnetic core from the rotor structure. Instead of using a separate non-magnetic core component, the rotor body itself is designed as a hollow cylindrical structure that directly serves as the mounting structure for magnets and rotor stack segments, eliminating the need for additional non-magnetic core material and reducing overall rotor weight.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges the functions of the non-magnetic core with the rotor body structure. The hollow cylindrical rotor body simultaneously provides structural support, magnetic path containment, and mounting surfaces for magnets and rotor stack segments, consolidating multiple functions into a single integrated component.

Inventive Principle:
Principle #5Merging (Combining)

2Stability of the object's composition

If a non-magnetic core is used in the rotor, then the structural stability is improved, but the number of components increases

Engineering Contradiction:
Improvestructural stabilityVSAvoidnumber of components
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The invention extracts and removes the non-magnetic core from the rotor structure. Instead of using a separate non-magnetic core component, the rotor body itself is designed as a hollow cylindrical structure that directly serves as the mounting structure for magnets and rotor stack segments, eliminating the need for additional non-magnetic core material and reducing overall rotor weight.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges the functions of the non-magnetic core with the rotor body structure. The hollow cylindrical rotor body simultaneously provides structural support, magnetic path containment, and mounting surfaces for magnets and rotor stack segments, consolidating multiple functions into a single integrated component.

Inventive Principle:
Principle #5Merging (Combining)

3Weight of moving object

If the rotor body is arranged close to the shaft, then the weight is reduced, but cooling capability deteriorates

Engineering Contradiction:
Improverotor weightVSAvoidcooling capability
Core Design Contradiction:
Weight of moving objectVSTemperature

Solution Approach 1:

The invention utilizes the radial dimension by creating a hollow cylindrical rotor body with an inner cavity that provides a cooling channel. This radial hollow structure allows cooling air to flow through the rotor body without significantly increasing the overall rotor dimensions or weight, effectively adding a cooling function in the radial dimension.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The invention implements a pneumatic cooling system by introducing cooling air channels through the hollow cylindrical rotor body. The inner cavity of the rotor body serves as a passage for cooling air flow, enabling effective thermal management through fluid (air) circulation without requiring additional heavy cooling components.

Inventive Principle:
Principle #29Pneumatics and hydraulics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design reduces weight and cost while effectively cooling the shaft and rotor body, enhancing magnetic properties and stability through separate elements and air-cooling, without the need for non-magnetic cores.

Implementation Method 1

the shaft and the rotor body can be cooled by air in the cavity

Methodology Applied
Scientific EffectConvection: Convection

Implementation Method 2

the shaft and the rotor body can be cooled by air in the cavity

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP4679677A1rotor
Publication Date: 2026.01.14 MAHLE INT GMBH
  • EP4679677A1 patent drawingFigure 1~2
  • EP4679677A1 patent drawingFigure 3~4
  • EP4679677A1 patent drawingFigure 5~6

AI summary

The invention relates to a rotor (1) for an electric machine, especially a spoke-type internal-permanent-magnet motor. The rotor (1) comprises a shaft (2) and an annular rotor body (3). The shaft (2) is arranged in the rotor body (3) at a distance, so that an annular cavity (8) is formed between the shaft (2) and the rotor body (3).